1. Field of the Invention
This invention pertains to agricultural implements, and more particularly to apparatus for applying fertilizers to fields.
2. Description of the Prior Art
Various equipment has been developed to spread fertilizer onto lawns, gardens, and fields. An especially important fertilizer-related machine is the manure spreader. Such machines are practically indispensable for transporting animal wastes from confined areas such as barns and barnyards and for recycling the wastes as fertilizer onto fields.
Manure spreaders invariably include a storage tank or box that is mounted on wheels for being pulled over the ground by a tractor. Manure spreaders also usually include an auger, conveyor, or similar device that propels the material to a discharge opening in the box. One or more rotary expellers are normally located at the discharge opening. The discharge opening and expellers are usually located on a side of the box near the front end of the machine. Material fed by the auger or conveyor to the discharge opening is accelerated by the expellers and flung a distance from the manure spreader, thereby spreading the material more or less evenly onto the surrounding field.
Examples of prior manure spreaders may be seen in U.S. Pat. Nos. 4,124,166; 4,473,184; and 5,085,372. The manure spreaders of the three foregoing patents, like the majority of commercial equipment presently available, include expellets that rotate about horizontal axes. Such machines, although in widespread use, are not completely satisfactory. They are able to handle liquid and semi-solid manure without problems, but they have difficulty in spreading solid or compacted material. A disadvantage of front discharge machines is that they must be operated with care to make certain the wind does not blow discharged material against the tractor.
U.S. Pat. No. 3,539,113 shows a manure spreader that has two flat disks that rotate about respective vertical axes. Material is fed by a conveyor to a discharge opening, whereat the material walls by gravity onto the rotating disks. The disks fling the material outwardly to spread it on the field. The disks are located relatively close to the ground, and therefore the spreading area is limited. In addition, the disks do not handle solid materials very well.
U.S. Pat. No. 4,350,303 describes a manure spreader that has two disks that rotate about respective vertical axes and also tined carriers concentric with and located above the disks. Long resilient tines reach through the storage box discharge opening and over the box floor. The tines occupy practically the entire area of a single large discharge opening The tines scrape material in the box and fling it outwardly through the discharge opening. Material that passes past the tines falls to the disks for being flung onto the fields. The device of the U.S. Pat. No. 4,350,303 patent requires the tine driving mechanism to produce considerable torque in order for the tines and carrier to accelerate material out of the box. In addition the tines are susceptible to malfunction due to improper and even permanent bending thereof during operation.
Many prior manure spreaders employ one or two augers for moving material to the discharge opening. U.S. Pat. No. 4,124,166 is a typical example of a dual auger machine. It is a difficult problem to design proper supports and restraints for augers in machines with discharge openings at the back end of their boxes. That is because it is desirable for the auger to terminate at the discharge opening, but placing a bearing there blocks flow of material through the discharge opening. Some prior machines are designed with augers that float within the box, but that solution is not considered satisfactory.
Another problem commonly encountered in manure spreaders is the tendency of solid material to bridge over the augers or conveyor. U.S. Pat. No. 5,085,372 shows a manure spreader with a side discharge opening. An auger has one end journaled in a vertically reciprocable plate located near the discharge opening. By raising and lowering the plate, the auger is tilted about its other end to break up the material. That design is not practical for manure spreaders having discharge openings at the back end of their boxes.
U.S. Pat. No. 4,597,532 shows a manure spreader with a material breakup device in the form of an oscillating arm. One end of the arm is pivotally connected to a side wall of the storage box. A hydraulic cylinder is used to oscillate the arm about an axis parallel to the direction of general movement of the material through the box. The oscillating arm penetrates the material to break it up and prevent bridging.
U.S. Pat. No. 4,850,515 discloses a small hopper for dispensing particulate materials in beverage machines. A helical auger is used to transfer material within a receptacle. A bar is cantilever mounted at one end to the receptacle. The other end of the bar has a finger that engages the auger. Rotation of the auger causes the finger to rise and fall and thus cause the bar to pivot in a plane generally parallel axis of the auger. Such an arrangement is satisfactory for small particulate dispensing machines, but it is entirely unsuitable for use with agricultural fertilizer spreaders.
Thus, despite the numerous kinds of machines available for discharging and spreading fertilizers, further improvements to such machines are needed.